Electric plug



Sept. 5, 1950 l LUDWIG ,ELECTRIC PLUG Filed July'8, 1947 Lay/5' Lao/405 IN VEN TOR.

Patented Sept. 5, i 1950 UNITED STATES PATENT: OFFICE w 7 .2521393 I v ELECTRIC PLUG Louis Ludwig, New York, N. Y. Application July 8, 1947,'S erial'No. 759,651

. 1 This invention relates generally to electrical attachment plugs and more particularly to thecontact elements thereof. I

Itis known to mount a plurality of contact elements upon a resilient plug body composed of insulating material, an example of which is seen in U. S. Patent No. 2,042,580, and it is among the principal objects of the presentinvention to provide improvements in the contact elements of the type shown in said patent.

, .Another object herein lies in the provision of contact element construction in which a reliable electrical connection, of substantially low resistance is obtained between a conductor and the contact element in the plug body. I

Another object herein lies in the provision of contact element construction invwhich a steady mechanical connection is obtained between, a conductor and said contact element so that'a desirable distribution of strain is produced when the conductor is subjected to pulling stresses whereby the tendency of the conductor to separate from the contact element is substantially reduced.

Another object herein lies in the provision of such construction and coordination of the parts that the conductor may be connected to the contact element in a rapid and convenient manner requiring a minimum of skill on the part of the operator and a minimum of special equipment. This results in a reduced manufacturing cost accompanied by wide distribution anduse.

An important feature of. the invention lies in the fact that the connection between the conductor and the contact element may be obtained by a clamping action and may be augmented by soldering in a convenient and low cost manner.

' Electrical attachment plugs composed of a molded insulating material which is vulcanized or otherwise integrated with the outer insulating covering of a cord composed of one or more conductors, are well known and have lproven satis factory in a considerable number of applications. In such constructions a considerable amount of pulling strainwhen the cord is tugged upon by the user is carried through the outer insulating covering directly to the plug bodyfwhich in turn is mechanically attached to the contact elements.

The integral molding of the cord covering and plug body is relatively expensive and prevents the 1 Claim. (01. 173-361)] usage similar to that in-Patent No. 2,406,144 but relates-to an improved construction. 1 These objects and other incidental ends and advantages will more fully appear in therprogressof this disclosure and be pointed out in the, appended claim.

In the drawings inence characters designate corresponding throughout the several views: 7 Fig. l is a front fragmentary view of a plug unit embodying the invention. Fig.2 is an enlarged fragmentary vertical 's'e'c tiona'l view of the device shown in Fig. I. Fig. 3iis a plan view of acontact element blank in one stage of the formation thereof.

which similar referparts cord and Fig.. 4 is an enlarged view in perspectiveof contact element in in Fig. 3. v

a stage followingthat shown Fig. 5 is a view in perspective takenfsimilarly to Figs 4, but showing the contact element conductorin an assembled condition. v I Fig.6 is a horizontal sectional viewfas" seen fromtheplanefiafi'on Fig.4s..

In accordance with the invention, the assen'i' bled-device or cord and plugunitjisgenerally indicated by reference Character l0, and ineludes broadly a cord H .containing. a plurality; of conductors l2 and I3; a plug body it; ends plurality of contactelements l5 and, I6. Y H, ,The cord Il may be of any suitablecharacterincluding the outer insulating covering IL and the-inner insulating coverings l8 and .IS which cover the individual conductors. l 2 and l3 ;respectively. a f

The plug body- I4 ispreferably composed ofresilient insulating material such-as rubberor synthetic rubber and includes a cord; passage 20,- hollow chambers 2| and 22, an insulating vein 23, and a. bottom wall 24. The bottom wall 25 is provided with orifices for passages-2 5 and JG throughwhich the contact elements ;I 5 and downwardly project. Thechambers 2| and 22 have'upper walls'Zl and 28and abutment por-' tions 29, 30, 3| and 32.

Since the contact elements l5 and IG'are sub stantially' identical, except that they "are oppo sitely arranged in position, a detailed description of one will suflice for all. As seen from Fig. 3, the blank'33 may be stamped and formed by suitably severing 'a continuous strip of flat stock, prefer ably of half hard brass so that'as aflected by the stamping and forming operations, the finished contact element may have the desired resiliency I and conductive properties. The blank" has side edge portions 34, 35, 36 and 31, rounded ends 38 and 39, usual holes 40 and H, retainerprojec' tions or tongues 42, 43, 44 and 45, a conductor entrance orifice 46, a, conductor exitoriflce l1 and a bending area 48 and, a tunnel-portion 50. "I'lie" verge downwardly at an acute angle 5 that the ends 38 and 39 contact. This distributes the strain when the blade members 54 and 55 arecompressed toward eacl'i other by insertion in a receptaclelnotshown) inv a well known manner; The effect just-describedimay'beincreasedby'giw fngth'e-end's 38 and; 39" an additional bend toward eachiotlcie'r the area at and below the" holes 48-.

and 41.. -'Ihis tends to increase theparallelism of.

the inner opposed surfaces of the blade members Stand '55 permitting. a slightly greater distance forinwandflexurea. 1 v

Assembly of a conductor, such as the conduc'. tor; iiiwith the: contact element L is preferably performed by stripping the inner insulating cove ering: -,l9-fromthe conductor It for a distance slightly in excessofthedistance between theorifi edfi andthe orifice and inserting the exposed conductor end. upwardly through the. orifice 46- alongthe groove .52 and out vthrough the. orifice 4-1..v Following this, the bend 53 is subjected to opposed lateral pressures as is also the exposed bulge 5i.- This pressure is suflicient to change the bfndi53i from the rounded form shown in Fi 4. to a relatively acute form shown in' Fig. 5. The pressure whichserves to make the bend; 53 more acuteis confinedclosely to the apex of the: bend so that the bowed effectseen. in Fig. 2 and Fig; 5 is. not'lojst; assures; that the blade elements 54f'fand55shajll'. remain in a spaced conditionallbwlng for inward flexure when the contact elements are engaged in a well knownr'eceptacle or socket (not shownr. Pressureinwardlyof'the contact element I6 is applied'also on the bulge 5Twhich causes the tunnel portion to flatten slightly or increase its cross sectional radius of curvature; The amount of deformation caused by the lastmention'ed pressure will depend on anumber of factors including the value of the pressure; thef'ormability arm-e stock'of-zwhich the contact element'l fi is composed; theeff-ective hullsv of the uninsulated end. 56 of the conductor" L3. This effective bulk' will be afiecte'd' by such considerations' as whether or not theconductor l3? is strained or" solid; and its gauge.

with the-parts assembled. as shown in Fig; 5;. considerable. mechanical pressure is-exerted upon: the uninsulated terminal 46; Withcertain gauges. of conductor, their predetermined thicknesses ofv inner --insulatmg; covering-,. a portion. of the: coveringrl fi: may be frictionallyretained within the-tun nel'i member or portion 50. The-substantially 180- degree bend'BT in: the conductor I3 and covering. I 9 produces a snubbing. effect which absorbs; teni sion uponthe conductor' l3.- upwardly as viewed imFig; 5 ret'arding. the transmission. of: such ten.- siontoethe area between the upper ends of. the blade-members and 5 5.'Wher.ethe electricallcontact is beingaobtained;

-Wheresit isdesired to-increase the. conductivity oi the,- electrical joint. between the uni-nsulatedl endl 5fi and; the contact element. lfi particularl'yaver longer periods of. time, and where a. surface oxidation orucorrosion: is to be;- prevented, the

t whole upper end extending preferably as far as the point 58 of the assembly of Fig. 5 may be clipped in flux and molten solder. During such a dipping the, conductor ,1 9; 1 of course, is rotated throu h approximately 1 80 degreesso that it lies along the outer surface of the blade member 54. -After assembly and fabrication of the contact elements or contact element units including a conductor and contact element in combination, they. may beassembled within the plugged body n in a well known manner. This may be done forexample; by: temporarily distorting the plug body and. drawing the parts into the body with suitable tools. As seen in Fig. 2, the retainer projections engage correspondingly positioned abutment portions while the conductor termirials '60 and c'l 'emb'ed themselves in the upperwalls 21 and 28 of the hollow chambers 21 and 22', This serves to further anchor the conductor with respect to the plug body, as well as to further anchor the contact elements with respect to'the plug bo'dyfor greater utility and durability It may thus be seen thatl have disclosed anovel and useful electrical attachment plug" construction which affords desirable electricaland' mechanical characteristics by which by virtue of the simplicity thereof may be manufactured in large scale. with substantially no increase over prior constructions of lesser effectiveness.

I wish it to be understood that I do not desire to. be limited tothe exact details of construction shown and described; for obvious modifications will'occu'rto a person skilledin theart.

In a. plug, a body' having a cord passage at one face leading to a central cavity with prong passagesl'eadi'ng through another face of the body; and prongs extending through said passages, each of'the prongsbeingformedof. a strip of'resilient metal bent upon. itself to form a bent'portion. and opposing. leg. portions, one of theleg, portions havinganentrance. wire orificathe bent portion of. the prong having. an. exit wire orifice, a. groove portion. in the one leg, leadingv from one orifice to the oth'en. a retainer projection on least one at the. leg. portions}. said. leg portions upon being restricted in the prongv passage serving to maintain a relatively acute bend! in the bent portion to flatten the. exit orifice and to bind a wire therein which. may be extended. into the entrance orifice and. along the groove and through. the exit. orifice. in. the. bent portion whereby the wire is resiliently engaged by the wall oil the groove and. the opposed leg portion, the opposed.- leg portions being resiliently spaced adjacent the outer end. of the prong. passage and. engagingwith one. another at'thei'r. outer ends.-

- LOUIS LUDWIG.

' REFERENCES CITED 1 UNITED STATES PATENTS Number I Name Y Date.- v

379,598 Otto Mar. 20,1888 115471762 I Wiseman. Nov; 1', 1927' .l',674,2'46 Gaynor et al. June 19', 1928 2,052,291 Killka May 21, 19.351 2,020,015 Boone Nov. 5', I935 2;U42',5 .Bernfeld June" 2; 1938 2,068,486 Gilbert Jan. 1'93 193 2,183,109 Sips Dec; 1 2", 19 39 2,406,144 I Herman Aug. 20'; I946 

